The invention relates to a grinding wheel and grinding system for grinding a blade in whose surface foreign ions are imbedded by a plasma-supported method, as well as a method of grinding such a blade with a grinding wheel.
In longitudinal- and cross-cutting machines for paper or cardboard webs or plastic or metal foils a steel blade is used whose surface has been treated to increase its wear resistance. Longitudinal web cutters have as is known pairs of rotating disk blades that cut longitudinally through the web. Transverse cutting machines for creating individual sheets from a material web have a transverse cutter with two blade drums each provided on its surface with one or move transverse blades extending the full length of the drum.
German patent application 198 40 950 describes a particularly advantageous blade for cutting moving material webs that has a blade with a steel cutting edge with at least the surface of the cutting edge coated by means of a plasma-supported method with foreign ions with a penetration depth between 50 xcexcm and 500 xcexcm, preferably 100 xcexcm to 200 xcexcm. Dosing the foreign ions in the metal lattice serves to improve the hardness of the cutter optimally without making the steel too brittle or influencing its ductility.
It has been shown in practice that the grinding of such a blade with the known grinding disks and grinding procedures is unsatisfactory, in particular the cutting edge fractures during grinding.
It is therefore an object of the invention to provide a grinding wheel, a grinding system, and a grinding method by means of which the blade of German patent application 198 40 ,950 can be ground to a higher quality.
The object is achieved by a grinding wheel which has as grinding medium silicon carbide in a particle size between 100 mesh that is imbedded in a ceramic-base binder with aluminum silicate, the grinding particles being thermally bound and hardened in the porous aluminum-silicate binder and the concentration of the grinding medium in the grinding wheel being more than 1% by volume.
Preferably the concentration of the grinding medium in the grinding disk is between 30 and 55% by volume and the pore volume of the binder is between 45 and 70% by volume.
The grinding system for achieving the second object uses a first grinding disk for coarse grinding with the above-described characteristics and a second grinding disk for polishing the cutting edge of the blade that has as grinding medium pure corundum with a particle size between 400 mesh and 800 mesh, preferably with an average particle size between 500 mesh and 700 mesh, in particular about 600 mesh.
Preferably the second grinding disk for polishing has a grinding medium that has a binder of a multicomponent synthetic resin, preferably a phenol, with a concentration of more than 1% by volume, preferably 30 to 50% by volume, and a polishing filler with a percent by volume of between 3% and 10%.
The method of grinding a blade to achieve the third object is carried out such that the blade is ground with a grinding disk according to one of claims 1 or 2 with a grinding speed of 5 m/sec to 15 m/sec, preferably 10 m/sec.
Preferably the blade is first coarse ground with a grinding wheel according to one of claims 1 or 2 with a grinding speed of 5 m/sec to 15 m/sec, preferably 10 m/sec, and then is polished with the second grinding wheel according to one of claims 3 or 5 with a grinding speed of 20 m/sec to 30 m/sec, preferably about 25 m/sec.